hi brian, i suppose halfway round the world aint bad for a small single, but, id hve hoped for more than 30k miles out of it. So heres my 2 cents/pence worth from the uk.

Do more oil and filte changes more often with more oil and filters.

1 ur original post; can i fix it with hand tools. You can take the motor out and strip it down, but it sounds like the crank is well and truly f*ck*d by now. Especially the journal shells, its possible this has caused "whip" in the crank that has eaten the cases. For education purposes buy a "haynes" manual and strip it down to investigate

Youve probly allready done this hence ur second post can i put new internals from a "good" engine into the old cases.

2 NO please dont do this, you may end up making a very short lived engine out of a good one. the crank journals are "line bored" that is each individual crank case is "drilled" (more relevant on multicylinder i guess) an then matched to a crank. if you bung in a diff crank you may well not meet the toleraces and the thing will eat itself. Also whats the point in maing work for yourself

3 Changing engine numbers is no big deal, engines do wear out they are consumable, i appreciate your desire to keep your docs straight. but it may not be sucha problem, you might even be able to change it online and get new docs sent from oz easily ?

4 I dont think you can get higher output stators, the drive gear on them si quite model specific. you can get higher capacity bateries, look for higher rating in Amp Hours, you could even wire up a second battery in parralel. that is switchable so you dont ever flatten your starter circuit using the fag lighter or whatever.

5 Also you can wire the the coils straight from the alternator/stator, keeping the original feed from cdi for the timing, to give you the biggest current your gonna get. run the lights off a relay, rather through the switchgear, again straight from alterator feed to fusebox, keeping wire length to minimum enabling use of thicker wire to get more amps to the bulb.

im no expert and i havent explained this stuff well but mail me if you want. There is a wiring diagram on oldskoolsuzuki.info that will help you if you want to make a new one. Youve probly found it but google thumpers.com or similar for better online tech

good luck